Removal of multiple impurities (SiO₂, Al, Fe, and Ni) from diamond wire saw silicon powder via BaCO₃-NaCl...

Although diamond wire saw silicon powder (DWSSP) represents a valuable silicon resource, its high-purity recovery is significantly hindered by a surface oxide layer (SiO₂) and metallic contaminants (Al, Fe, Ni). Current recycling strategies face challenges in achieving high silicon recovery percentage while simultaneously eliminating multiple impurities. In this study, a chlorination refining process utilizing a BaCO₃-NaCl system is proposed to simultaneously eliminate SiO₂, Al, Fe, and Ni. Thermodynamic calculations were performed to predict the reaction behaviors of impurities, followed by experimental validation to assess the impurity removal efficiencies and silicon recovery percentage. Thermodynamic analysis indicates that BaCO₃ initiates the reaction with SiO₂ at 600 K, making the removal of the oxide layer theoretically feasible. As the temperature increases to 1100 K, BaCl₂ and Na₂O are formed as intermediate products of the interaction between BaCO₃ and NaCl, and at 1800 K, BaCO₃ decomposes into BaO. SiO₂ can react with Na₂O and BaO respectively, while Al₂O₃ can react with BaCO₃, Na₂O, and BaO respectively. Experimental results demonstrate that under the optimal weight ratio of DWSSP : BaCO₃ : NaCl 100: 7.38: 10, the silicon recovery percentage reaches 93.10%. Simultaneously, significant removal efficiencies for Al, Fe, and Ni impurities are achieved at 75.00%, 91.01%, and 78.66%, respectively. This study confirms that the proposed BaCO₃-NaCl refining strategy effectively facilitates the simultaneous deep removal of oxide and metallic impurities. It offers a technically feasible and high-recovery solution for the value-added recycling of DWSSP waste.